imagex /mountrw D:\MyBackup.wim 1 C:\MountFolder
To create a backup or a deployment image of a drive (e.g., your C: drive), use the /capture command. It is best to do this from a bootable environment like to ensure files are not in use. Download File ImageX v1.3.rar
If you prefer a visual interface over the command line, GImageX is a popular, free graphical frontend for ImageX. imagex /mountrw D:\MyBackup